Fixes https://github.com/zed-industries/zed/issues/33257

Previously, the scale-factor-change-handling logic relied on
`SetWindowPos` enqueuing a `WM_SIZE` window event. But that does not
happen when the window is maximized. So when the scale factor changed,
maximized windows neglected to call their `resize` callback, and would
misinterpret the positions of mouse events.

This PR adds special logic for maximized windows, to ensure that the
size is updated appropriately.

Release Notes:

- N/A